The present invention relates to electrically operated valves, and particularly valves for controlling water inlet flow to appliances. The invention particularly relates to valves employed for controlling water inlet flow to clothes washing machines and dishwashers.
In such household appliance applications, valves of this type typically are energized by a programmer/timer which controls the appliance duty cycle; appliances of this latter type usually have relatively high water inlet flow requirements requiring a suitably sized flow area through the valve to provide the required flow at the lower end of the supply pressures usually encountered in residential service, which may be as low as 15 PSIG (103 kPa). When sufficient flow area is provided for the valve at the lower supply pressures encountered in service, the force of the inlet supply pressure acting across the movable valve operator member requires a substantial current flow in an electric operator to effect opening of the valve against the force of the supply pressure. Therefor, it has been the practice in designing appliance water inlet valves to utilize a pilot operator having a small area exposed to the supply pressure. The use of a pilot operator enables a low force electrical actuator to create flow from a pilot chamber which, in turn, creates a pressure imbalance on the main valve operator and allows the integrated force of the pressure differential created thereacross to effect opening of the main valve.
Heretofore, it has been common practice to employ a ferromagnetic pilot valve member in a pilot operated electric appliance water inlet valve, and to effect movement of the pilot valve member by the magnetomotive force generated from an electromagnetic actuator, typically a coil surrounding the pilot valve member. In order to effectively utilized an electromagnetically actuated pilot valve, it is necessary to have a portion of the pilot valving chamber formed as a guide such as a tubular guide for directing the movement of the pilot valve between its open and closed positions. In such an arrangement, the limited clearance between the pilot valve member and its surrounding guide has created problems where sand or other foreign particles in the water supply become lodged between the pilot valve member and its guide, thereby rendering the pilot valve immovable in either the closed or open position, in the case where the pilot valve is immobilized in the open position, flooding of the appliance and the surrounding premises can be the result.
Heretofore, pilot operated electric appliance inlet valves have employed a flexible diaphragm as the main valve member. It is known in such a valve to use a rigid insert disposed centrally through the diaphragm and also it is known to have the pilot flow passage formed through the insert with the pilot valve seat provided on the insert on one side of the diaphragm. Where this arrangement is employed, movement of the main valve member upon opening causes relocation of the pilot valve seat. In turn, this requires that the movement of the diaphragm insert be guided in order to maintain the pilot valve seat aligned with respect to the pilot valve member to insure accurate closing of the pilot valve member upon de-energization of the electromagnetic actuator. Thus, it has been desired to provide a way or means of providing guidance for the diaphragm insert which forms the pilot valve seat, and yet prevent lodging of the insert in the guide in the presence of foreign particles such as sand.
Heretofore, in pilot operated electric inlet valves, it has been the practice, where a flexible diaphragm is employed for the main valve operator, to provide replenishment flow to the pilot valving chamber through one or more bleed-flow holes having very small diameter formed through the diaphragm and insert. This arrangement has proven to be troublesome and a source of clogging by foreign particles such as sand, which may be present in the water supply. Furthermore, it has proven to be extremely difficult and costly to manufacture in high volume production the flexible diaphragms with the precision control of the small bleed holes for controlled flow through the flexible diaphragm to replenish the pilot chamber.
Therefor, it has long been desired to provide a way or means of providing bleed flow to the pilot valving chamber remote from the flexible diaphragm valve member. It has also been desired to provide adequate filtering of the bleed flow to the pilot chamber to prevent clogging due to foreign particles such as sand in the water supply.